Temperature controlled device



y 25, 1965 E. H. LUSEBRINKQ 3,185,816

TEMPERATURE CONTROLLED DEVICE Filed Aug. 30, 1965 Vll llllll ELECTRODES l9 I8 F l G. 3 EMBEDDED IN INSULATION I8 I? INVENTOR ELMER HENRY LUSEBRINK ATTORNEY 'by means of steam or electric heaters.

United States Patent 0 This invention relates to a device embodying a temperature controlled process roll for thermally treating moving webs and to a novel temperature controlled roll.

Heated rolls are widely used in a number of diitferent web processing machines in a variety of industrial applications. For example, many calendering and laminating operations, treatments of textiles, drying of paper webs, etc. rely on the use of'hea-ted rolls. Generally, these rolls are of considerable mass and are designed to maintain a certain elevated temperature over a long period of time to afford a uniform treatment of a web of great length. Such rolls are usually heated internally In applications Where repeated, short, intermittent, thermal web treatments of only a few seconds duration are required these rolls do not perform satisfactorily. They require relatively long heat-up times and, because of their mass and heat capacity they maintain the elevated temperature for a considerable length of time after the heating means is deactivated.

It is therefore an object of this invent-ion to provide webprocessing rolls having rapid-heating characteristics. It is a further object to provide such rolls that have a low heat capacity and will cool rapidly when the heating means is turned off. Another object is to provide such rolls that are self-regulating and maintain a desired temperature within narrow limits. A still further object is to provide such rolls that can go through a succession of short hot and cold cycles. Another object is to provide such rolls that have minimum deflection under a uniform load and have a hard, smooth surface. Another object is to provide a highly efficient thermal roll where the temperature is not greatly elfected by the duty cycle, varying thermal loads, and varying supply voltages.

Yet another object is to provide such rolls that are inexpensive, operate on normally supplied electric current,

are easy to manufacture, and require little or no maintenance.

The temperature controlled device of this invention comprises a frame member which supports a hermetically sealed rotatable hollow roll having a lining of dielectric material on its inner walls, electrodes embedded in the lining with their outer surface exposed to the hollow interior of the roll, and insulated leads extending from the electrodes to conductor elements outside the roll, said roll containing small, measured amounts of an electrically conductive liquid of low vapor pressure which is liquid at 25 C. at normal pressure and exists in the form of a vapor at 50481) C. The roll preferably is metal.

In another important aspect of the invention, the temperature controlled device has, in combination with the process roll, a pressure roller, preferably having a heatresistant, resilient surface which is adapted to press against the process roller and rotates therewith.

The process roll of this invention is useful for many applications where a moving Web must be thermally treated. The roll is particularly useful in office copy machines of the thermal transfer type in which an image of an original is produced on a receptor sheet by performing a thermal transfer operation from a selectively photopolymerized matrix material. A machine of this type is disclosed in assignees copending patent applications, Heiart and Velvel, Serial No. 234,616, filed Nov. 1, 1962, and Cohen, Serial No. 250,856, filed I an. 11, 1963.

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In these machinesthe thermal process roll is mounted such that it is rotatable only when it is in contact with the moving matrix and a rotating pressure roller. Suitable photopolymerizable matrix materials for use in such machines are disclosed in US. Patent Burg and Cohen, 3,060,- 023 issued Oct. 23 1962, and US. patent applications Burg and Cohen, Serial No. 163,078 filed Dec. 2-9, 1961; Heiart, Serial No. 123,651, filed July 13, 1961; Cohen and Luebbe Serial No. 156,518, filed Dec. 1, 1961; and Burg Serial No. 234,214, filed Oct. 30, 1962.

The invention is best explained by means of the attached drawings which are part of this specification and in which:

FIG. 1 is a front elevation of the temperature controlled device in combination with a pressure roller,

FIG. 2 is an end elevation of the device of FIG. 1,

FIG. 3 is an enlarged elevation of the process roll with parts in section, and a portion in enlarged section, and

FIG. 4 is a cross-sectional enlarged view of a portion of the roll showing the electrodes in the form of a helix.

With reference to the accompanying drawing, wherein the same reference numerals refer to the same parts throughout the several views, a practical temperature controlled device of the invention has a frame base 11 and spaced end standards 12 which may be integral with the base or separate and afi'ixed thereto in any suitable manner, e.g., by weldments, machine screws or bolts, or by dovetailing ends and coacting grooves in the base frame. The end standards contain suitable bearing blocks 13 in which the laterally extended journal ends 14 and 15 of hermetically sealed hollow metal roll 16 are adapted to respectively rotate. The roll consists of a hollow metal tube which has end plates 17. The inner walls of the roll including both the circumferential walls and the end walls are provided with a layer 18 of thermally conductive dielectric material. This material as well as the journal end plates can be made of a phenol-formaldehyde, an epoxy or a silicon resin which; may contain mica particles or fiber glass. A pair of spaced electrodes 19 which are very narrow in cross-section and in close proximity to each other are imbedded in the layer of dielectric material. The outer surfaces of the electrodes, however, are not coated or covered with the dielectric material and with it form the inner surface of the fabricated metal roll. Leads 20 extend from the electrodes through the ends'of the metal roll and the outer ends of these leads are attached to suitable electrical conductor elements 21, which, as shown in FIG. 3, are composed of two spaced slip rings 21 and 21.

As also shown in FIG. 3, the journal end on the left of the metal roll is preferably made of rigid dielectric material which is both a thermal and electrical insulator. Thus, it can be composed of a suitable resin, e.g., polytetrafluoroethylene or of a mixture of a silicone and fiberglass, etc. In order to give greater strength and rigidity to the journal end 14, it may. contain a reinforcing metal tube 22. The leads from the electrodes to the outer conductor elements pass through a suitable seal, e.g.,rnetalglass seal 23.

The opposite journal end 15 need not be composed of dielectric material but can consist of a hollowmetal tube as shown. The outer end of this journal is provided with a screw threaded block 24 through which extendsadjust- 3 regulate the temperature of the roll in accordance with volume.

Surrounding the journal ends 14 and 15 respectively are insulating endplates 31 which can be fastened to the ends of the roll in any suitable manner, e.g., by means of a heat-resistant adhesive, etc. These insulating plates can be made of an asbestos composition, or a suitable synthetic resin or polymer, e.g., a phenolformaldehyde resin,

polytetrafluoroethylene, etc. These insulating plates reduce the heat loss of the roll.

Various conductive liquids can be added to the water introduced into the hollow roll. The additives can be acids or bases. Suitable acids include sulfuric, hydrochloric and nitric acid. Suitable bases includes sodium hydroxide and potassium hydroxide.

Contained within the sealed roll cavity is a small, measured amount of conductive liquid 29 preferably of low vapor pressure. The amount of liquid to be used can be determined mathmetically. For example in a roll with a 0.5 inch inside diameter, 10 inches long, where a temperature of 130 C. (266 F.) is desired with water having an absolute pressure of 39.18 lb./in. at 130 C. used as the liquid, the quantity can be determined by the following:

V 1 Pounds of water requ1redo q where V equals the specific volumes of the roll cavity in cubic inches, V is a conversion factor, and V is a property of the saturated vapor in cubic feet per pound as found in the steam tables. Thus the pounds of water required would equal 1728 X 1070 pounds or 0.00293 in. (0.0475 cm?) of water at 60 F.

The electrical circuit that supplies the power to the slip rings should contain an external resistance (not shown) to limit the current input to a value that is safe for the electrodes or grids used. This will prevent the passage of a high current through the electrodes and the resulting damage due to IR heat. Another method of preventing damage to the electrodes would be to have the electrodes connected to two slip rings on each roll end. This would supply two current conduction paths. The voltage used should be kept below the breakdown point, i.e., kept below the gas phase conduction voltage.

Pressure roller 30 preferably having a surface of yieldable material, such as a felt-covered or silicone rubber coated steel roll, can be supported in the frame by means of suitable bearings. The covering of the roll should have low thermal conductivity, low thermal capacity, and resist degradation at elevated temperatures. The pressure roll is positioned so that it would be in surface contact with the thermal roll 16. If desired, the pressure roll can be spring loaded by suitable means to insure good contact with the thermal roll.

In this embodiment, the thermal process roll is rotated by having the rotating pressure roll brought into contact with the thermal roll surface. Other methods of imparting motion to the thermal roll are obvious to those skilled in the art, For example, a gear could be mounted on the thermal roll shaft and the roll driven by a gear means, or a pulley could be mounted on the shaft and a belt drive means used.

During operation, the slip rings are excited from a supply source (not shown) and current is applied to the electrodes. The conductive liquid, which bridges the electrodes at various points, is then flashed into a vapor. The vapor recondenses upon contact with the cold tube wall. Since this is an electrode area also, liquid is refiashed into a vapor again. This process repeats until the liquid is completely converted to vapor and retained in that status; thus the roll temperature will be determined by the vapor temperature at equilibrium pressure. The heat produced by the liquid to vapor phase change is conducted to the thermal roll surface where it can be used for a thermal process. If a local exterior load, such as a moving web, is impressed on the roll, cooling an area, condensation and thermal make up occurs within the roll at that spot only.

The roll of this invention should be a good thermal conductor and sufficiently rigid to withstand the applied pressure loadings without undue deflection. A roll of stainless steel, brass, aluminum, glass or fiber glass/ plastic material is useful.

In applications where the surface area to be covered by the electrodes is small and a long length of electrode will not be necessary, the helically wound electrodes can be used. If the length of the electrodes becomes very large, the resistance of the electrode will become an important factor. In this situation it would be preferable to use a grid type electrode to cut down the length and resulting resistance. The grids of the electrodes located on the surface of the layer of epoxy resin within the roll cavity must be very narrow, closely spaced, and insulated from each other and the tubing wall. This design insures that when the vapor condenses the liquid droplets will bridge parts of both electrodes. These electrodes can be applied to the insulation layer by printed circuit tech niques. Ideally, all of the surface of the roll cavity should be covered with the electrode pairs, closely spaced. The electrodes could be made of copper, stainless steel, silver, or aluminum. The material used should take into consideration the chemical action of the liquid that will be placed in the roll cavity. In the preferred embodiment the electrodes should be flush with the surface of the insulation layer.

The liquid within the roll cavity performs two functions, its change from a vapor to liquid phase provides the required roll heat and the amount of liquid within the cavity determines the temperature the roll will achieve. The liquid used must conduct electricity and preferably have a low vapor pressure. If desired, a conductive additive such as an acid may be added to the liquid, but the additive must be one that will not precipitate onto the conductors during the phase changes of the liquid. Some liquids that may be used are Water, propyl-alcohol, methyl chloride, acetone, xylene, p-cymene, and ethyl chloride. The liquid selected should have as large a liquid volume as is possible with respect to the desired vapor pressure point. Also it should have a high conductivity of electricity as this enables a rapid phase change.

In a roll made of #316 stainless steel, 10 inches long and having an inside diameter of 0.40 inch and an outside diameter of 0.50 inch, the inside of the roll cavity covered with electrodes with a cross section of .010 inch x .005 inch spaced .016 inches apart, the roll cavity containing 0.0475 in. of water, and the electrodes having an input of 110 volts at 8.8 amperes; the roll would achieve a temperature of 100 C. within 1 to 2 seconds if the roll operated at approximately efiiciency.

In the described roller the temperature to be obtained is dependent upon the volume of the roll cavity and the liquid used. In applications where it is desirable to have a roller that will produce more than one temperature, a temperature adjustment device is necessary. As the temperature reached is a function of the pressure of the liquid within the sealed cavity, a means that varies the volume of the roll cavity will regulate the temperature produced within a range dependent upon the volume change.

The process roll system of this invention has many advantages over the prior art. The rolls are rapid-heating, self-regulating, and maintain a uniform temperature over the surface of the roller. They are relatively inexpensive, but highly eflicient. The control circuitry is simple, small, of low weight and can be adapted easily to small equipment. The roll system can handle webs of any length, single sheets or rolls. The temperature is controlled according to the demand, so that heating cycles of a few seconds or of any longer time can be maintained.

Many other modifications within the scope of the pres ent invention will be obvious to those skilled in the art.

I claim: A

1. A temperature controlled device comprising a frame member which supports a hermetically-sealed, rotatable hollow roll having walls or low heat capacity and a lining ofdielectric material on the entire inner surfaces of said walls, spaced electrodes embedded in said lining with their outer surfaces exposed to the hollow interior of the roll, said electrodes being distributed over the entire inner wall surfaces of the roll so as to permit operation of the device in any disposition or orientation of the roll, and insulated leads extending from the electrodes to conductor elements outside the roll, said roll containing small, measured amounts of an electrically conductive liquid of low vapor pressure which is liquid at 25 C. at normal pressure and exists in the form of a vapor at a temperature within the range from 50 C. to 180 C.

2. A device according to claim 1 wherein said liquid is water containing a conductive agent.

3. A device according to claim 1 wherein said electrodes are'in the form of a helix and said conductor ele ments are spaced metal slip rings.

4. A temperature controlled device comprising a base frame, spaced standards supported by said frame and, journalled in said standards, a small hermetically-sealed rotatable hollow metal roll having thin walls of low heat capacity and a lining of dielectric material on the entire inner surfaces of said walls, spaced electrodes embedded in said lining with their outer surfaces exposed to the hollow interior of the roll, said electrodes being distributed over the entire inner wall surfaces of the roll so as to permit operation of the device in any disposition or orientation of the roll, and insulated leads extending from the electrodes to conductor elements outside the roll, said roll containing small, measured amounts of an electrically conductive liquid of low vapor pressure which is liquid at 25 C. at normal pressure and exists in the form of a vapor at a temperature within the range from 50 C. to 180 C.

5. A temperature controlled device comprising a frame member which supports a hermetically-sealed, rotatable, hollow metal roll of low heat capacity and a lining of dielectric material on the entire inner surface of said walls, spaced electrodes embedded in said lining with their outer surfaces exposed to the hollow interior of the roll, said electrodes being distributed over the entire inner wall surfaces of the roll so as to permit operation of the device in any disposition or orientation of the roll, and insulated leads extending from the electrodes to conductor elements outside the roll, said roll containing small, measured amounts of an electrically conductive liquid of low vapor pressure which is liquid at 25 C. at normal pressure and exists in the form of a vapor at a temperature within the range from C. to 180 C., and a yieldable pressure roller adapted to press against the surface of said roll and rotate in synchronism therewith.

6. A temperature controlled device comprising a base frame, spaced standards supported by the base frame, and journalled in said standards (a) a small, hermetically-sealed rotatable hollow metal roll having thin walls of low heat capacity and a lining of dielectric material on the entire inner surfaces of said walls, spaced electrodes embedded in said lining with their outer surfaces exposed to the hollow interior of the roll, said electrodes being distributed over the entire inner wall surfaces of the roll so as to permit operation of the device in any disposition or orientation of the roll, and insulated leads extending from the electrodes to conductor elements outside the roll, said roll containing small, measured amounts of an electrically conductive liquid of low vapor pressure which is liquid at 25 C. at normal pressure and exists in the form of a vapor at a temperature within the range from 50 C. to 180 C., and (b) a yieldable pressure roller adapted to press against the surface of the roll and rotated in synchronism therewith.

7. A device according to claim 6 wherein said electrodes are in the form of a helix and said conductor elements are spaced metal slip rings.

References Cited by the Examiner UNITED STATES PATENTS 1,350,586 8/20 Xardell 219-284 1,987,119 1/35 Long 219--325 2,011,748 8/35 Boyd 219469 2,474,759 6/49 Schmitz 219-295 FOREIGN PATENTS 324,801 9/30 Germany.

RICHARD M. WOOD, Primary Examiner. ANTHONY BARTIS, Examiner. 

1. A TEMPERATURE CONTROLLED DEVICE COMPRISING A FRAME MEMBER WHICH SUPPORTS A HERMETICALLY-SEALED, ROTATABLE HOLLOW ROLL HAVING WALLS OR LOW HEAT CAPACITY AND A LINING OF DIELECTRIC MATERIAL ON THE ENTIRE INNER SURFACES OF SAID WALLS, SPACED ELECTRODES EMBEDDED IN SAID LINING WITH THEIR OUTER SURFACE EXPOSED TO THE HOLLOW INTERIOR OF THE ROLL, SAID ELECTRODES BEING DISTRIBUTED OVER THE ENTIRE INNER WALL SURFACES OF THE ROLL SO AS TO PERMIT OPERATION OF THE DEVICE IN ANY DISPOSITION OR ORIENTATION OF THE ROLL, AND INSULATED LEADS EXTENDING FRO THE ELECTRODES TO CONDUCTOR ELEMENTS OUTSIDE THE ROLL, SAID ROLL CONTAINING SMALL, MEASURED AMOUNTS OF AN ELECTRICALLY CONDUCTIVE LIQUID OF LOW VAPOR PRESSURE WHICH IS LIQUID AT 25*C. AT NORMAL PRESSURE AND EXISTS IN THE FORM OF A VAPORT AT A TEMPERATURE WITHIN THE RANGE FROM 50*C. TO 180*C. 